The present invention is directed to a porous structure having good insulating power coupled with mechanical stability, resistance to pressure, stability to environmental conditions and ready ability to be anchored to conventional roofing membranes. The claimed structure is a porous board formed from an asphaltic composition described in detail below which is capable of being applied to the exterior of structural surfaces, such as roofs, to provide insulation to such structural surfaces and to the compartment interior thereto.
Although the porous structure of this invention shall be described herein in terms of a porous board-like structure capable of use as a part of a structural roof formation, porous structures of other shapes and for other uses can be readily envisioned from the description herein below.
Built-up roofing has been employed for many years wherein a roof deck supports a membrane which prevents penetration of moisture. Such water impermable membranes have been formed from conventional asphaltic and bituminous compositions, laminates of asphaltic or bituminous material with fibrous products, such as roofing felt, or from rubberized asphalt sheet waterproofing membranes. Insulation is normally placed directly below the roof deck on the interior of the building to aid in maintaining constant and comfortable temperature therein.
Recently, it has been found that installation of insulation material on top of the exterior surface of a roof membrane provides the advantage of maintaining the applied waterproofing membrane at a more constant temperature and, thus, causes longer life to the membrane. Such roof structures have been dubbed "upside down roofs". These roof structures are formed by first applying a waterproofing asphaltic membrane, and then applying an insulating material, such as a foam sheet product, over the membrane. The foam sheet is anchored by the use of a mastic applied to the membrane and by placing gravel, large aggragate and the like over the insulation board.
The upside-down roofing system has not met with extensive acceptance in the industry even though it has the advantage of enhancing the durability and life of the waterproofing membrane. The lack of acceptance can be traced to the insulating sheet products presently used. These products are not capable of being stable and durable upon exposure to environmental conditions such as ultraviolet radiation from the sun's rays, moisture penetration from rain and snow and to temperature variations. Further, due to the difficulty in providing an anchoring mastic which is compatible with respect to both the asphalt membrane and the insulting foam material, the foam has been found to raise away or move from the membrane and thereby reduce its effectiveness. Finally, some of the presently known insulation materials have low crush strengths which do not permit working or even walking on the final roof structure once the insulation is applied.
An object of the present invention is to provide a foam product highly suitable for forming an insulation layer of an upside down roofing formation. The foam product is capable of exhibiting a high degree of stability to environmental conditions, a high crush strength or resiliency and a ready ability to be adhered to asphaltic roofing membranes by mutually compatable mastics.
Another object is to provide a stable foam product formed from a composition composed of asphalt and a polyvalent metal salt of certain sulfonyl or carboxyl groups containing polymers and preferably, in addition, a polymeric hydrocarbon. The foam product has a bulk density of less than about 9 pounds per cubic foot and a pore volume of at least about 85 percent.
Still another object of the present invention is to provide an improved roof structure formed from a roof deck having a conventional asphaltic waterproofing membrane thereon and having foam boards of the present invention applied to the free surface of the membrane.